I am by no means even remotely an experienced trader, but I wanted to mention something because it's a mistake
I made when I first got into post-searing Ascalon.
As someone said, if you're just in Ascalon, it's pretty likely that everything you pick up should go straight to the merchant. I'm guessing that the reason you couldn't get near the prices listed here for your mods is because
you don't have max mods. Modifiers come in ranges... like
up to +7 armor,
up to 20% chance,
up to +30 health, etc.
If your mod is not giving the maximum benefit as listed on the pages linked to in
this table on the Wiki, then you may as well save the salvage kits and just merch the weapon "as is." A bow grip of Fortitude is worth something if it's the full +30, but you're
extremely unlikely to find a buyer if it's like +24.
Personally, I reserve (most) of the max modifiers I know people look for, and keep them in my storage to sell... I make a few extra platinum here and there doing that and right now I can afford the storage space. I keep some of the less-than-max (like a fortitude +29 health) for my use... adding it to one of my heroes' weapons, for example. I'm not at the point where I can afford/have found any amazing uber weapons to be offering my heroes, so the less-than-perfect mods on their less-than-perfect weapons works for me right now.
Inscriptions, it's worth noting, work the same way... it's got to be maxed (with one or two extremely rare exceptions) or it's not worth bothering with.
As I said, this was not something I realized when I started... but several hours of dedicated "trade watching" in Lion's Arch and Kamadan helped me learn a bit more about what people wanted in terms of mods... and I've made a good start in building my bank thanks to that.